To "interconvert" motions is clarified as follows: Inter is an indicator meaning "mutually" which means "directed and received in equal amounts," and convert means to "change." Thus, to interconvert motions is to "mutually change motions," "equally change motions," "direct and receive motions in equal amounts," or "equally displace motions."
Motions of previously known drive systems cannot interconvert due to combinations of normal, environmental discrepancies such as backlash, slipping, stretching, unavoidable tolerance deviations, tangency misalignments, etc. With such discrepancies motions obviously convert (change) but they cannot interconvert (mutually change).
Consequently, if drive systems have been used as measuring systems for producing linear measurements, because measurements made by a drive's linear element are calculated from rotations made by its rotary element, discrepancies inbetween cause the measuring system's calculated measurements to be incorrect. This age-old problem is corrected with this invention by interconverting linear and rotary motions and therefore producing precision linear measurements over long distances.
At the National Bureau of Standards, the Dimensional Metrology Laboratory there utilizes an interferometer. With it, under environmentally controlled conditions measurements to approximately 200 inches long may be produced using light waves. The wavelengths of distances are counted with computer assisted techniques producing finite measurements which may be certified. Components may be measured there and certified, if required, to be accurate within several millionths of an inch. By contrast, within industry it is well known that the capability to produce measurements within a tolerance range of about 0.001 inch at extended lengths beyond relatively few inches is virtually unknown.
Devices such as large calipers or bow micrometers have "resolution" factors that are "graduated" to read 0.001 inch or less when extended to the lengths described. No assurances however are implied that the dimensions will actually be as read. For example, any two scales having similar divisions may be meshed and visibly witnessed that every indicant does not align. All scales are like this. When such indicia are then aligned with others, and used to facilitate vernier measurements, there exists no common denominator to determine the accuracy of the measurements. If using a bow micrometer, other length standards must be used in conJunction presenting other difficulties that again often negate desired measurement precision.
The above conditions have always plagued machinists, few of who will trust finite measurements as explained made with the devices described. Other means are employed to match-fit components, and many machinists will not accept such Jobs. Because of these conditions it is well known among design engineers that machining operations requiring finite measurements will entail additional expense. Therefore, wide latitude is afforded such problematic designs. Despite preferences to obtain accuracy it has become custom to design around such problems. In many instances consequences are parts which do not fit; requirements for hand operations, with increased costs being inherent rather than being able to depend upon less costly production techniques; and weakened structures due to the build up of tolerances made necessary and purposefully incorporated with design reconciliations.
As well as producing finite measurements at extended distances, computer aided design and drafting (CADD) are technologies with which the measurement digitizer of this invention may also be used. With these sciences the measurement problems indicated have thus far been avoided using other techniques. A popular technique uses a surface beneath which a printed circuit is embedded, and that has vertical and horizontal wires spaced about 0.010 inch apart. Through electrical induction with a pen-like instrument slid along the surface, analogous cross hair lines are displayed by a CRT. Other data entry mechanisms are the typewriter-like keyboard, light pen, cursor arm, tract ball, Joystick, thumbwheel and more. The measurement digitizer differs from these devices in that it may also be used directly with machine tools and for fabricating precision measurements.